How to change label based on day?

Hey guys. Sorry for my English.
I'm new to VB.Net (and programming in general) and I'm making a simple program where I work with the help of the internet.

I have a prominent Label at the top of this program, and I need it to be shown only on certain days, ie:

If today is the 1st, 5th or 16th (of any month) Label1 displays the message "ALERT! Today has a monthly schedule!"

If today is (last day of current month), 04 or 15 (of any month) Label1 displays the message "ALERT! Monthly schedule for dawn!"

Can anyone help me build this? Thank you.